using Microsoft.Data.Sqlite;

namespace WheresMyMoney.Maui.Core;

public class Repository
{
    private static Repository? _instance;

    public static Repository Instance
    {
        get
        {
            if (_instance is not null) return _instance;
            string dbPath = Path.Combine(FileSystem.AppDataDirectory, "wheresmymoney.db");
            _instance = new Repository(new SqliteConnection($"Data Source={dbPath};"));
            return _instance;
        }
    }

    private readonly SqliteConnection _connection;

    private Repository(SqliteConnection connection)
    {
        _connection = connection;
        _connection.Open();
        CreateTables();
    }

    ~Repository()
    {
        _connection.Close();
    }

    public void CreateTables()
    {
        using var command = _connection.CreateCommand();
        command.CommandText = """
                              CREATE TABLE IF NOT EXISTS planned_payment (
                                  id INTEGER PRIMARY KEY AUTOINCREMENT,
                                  amount INTEGER NOT NULL,
                                  name TEXT NOT NULL,
                                  date_start TEXT NOT NULL,
                                  date_end TEXT NULL,
                                  is_subscription BOOLEAN NOT NULL,
                                  reoccurences INTEGER NULL,
                                  reoccurence_type INTEGER NULL CHECK(CASE reoccurences IS NOT NULL AND reoccurence_type IS NOT NULL WHEN TRUE THEN is_subscription ELSE NOT is_subscription END)
                              );

                              CREATE TABLE IF NOT EXISTS balance (
                                  id INTEGER PRIMARY KEY AUTOINCREMENT,
                                  amount INTEGER NOT NULL,
                                  date TEXT NOT NULL
                              );

                              CREATE TABLE IF NOT EXISTS settings (
                                  id INTEGER PRIMARY KEY AUTOINCREMENT,
                                  payday TINYINT NOT NULL CHECK(payday BETWEEN 1 AND 31)
                              );
                              """;

        command.ExecuteNonQuery();
    }

    public void InsertPlannedPayment(decimal amount, string name, DateTime dateStart, DateTime? dateEnd,
        bool isSubscription,
        int? reoccurences, ReoccurenceType? reoccurenceType)
    {
        using var command = _connection.CreateCommand();
        command.CommandText = """
                              INSERT INTO planned_payment (amount, name, date_start, date_end, is_subscription, reoccurences, reoccurence_type)
                              VALUES (@amount, @name, @date_start, @date_end, @is_subscription, @reoccurences, @reoccurence_type);
                              """;

        command.Parameters.AddWithValue("@amount", (int)(amount * 100));
        command.Parameters.AddWithValue("@name", name);
        command.Parameters.AddWithValue("@date_start", dateStart);
        command.Parameters.AddWithValue("@date_end", dateEnd.HasValue ? dateEnd.Value : DBNull.Value);
        command.Parameters.AddWithValue("@is_subscription", isSubscription);
        command.Parameters.AddWithValue("@reoccurences", reoccurences is null ? DBNull.Value : reoccurences.Value);
        command.Parameters.AddWithValue("@reoccurence_type",
            reoccurenceType is null ? DBNull.Value : (int)reoccurenceType.Value);

        command.ExecuteNonQuery();
        
        DataChanged(this, EventArgs.Empty);
    }

    public void InsertBalance(decimal amount, DateTime date)
    {
        using var command = _connection.CreateCommand();
        command.CommandText = """
                              INSERT INTO balance (amount, date)
                              VALUES (@amount, @date);
                              """;

        command.Parameters.AddWithValue("@amount", (int)(amount * 100));
        command.Parameters.AddWithValue("@date", date);

        command.ExecuteNonQuery();
        
        DataChanged(this, EventArgs.Empty);
    }


    public decimal GetNewestBalance()
    {
        using var command = _connection.CreateCommand();
        command.CommandText = @"SELECT amount FROM balance ORDER BY date DESC LIMIT 1;";
        var result = command.ExecuteScalar();
        return result != null ? Convert.ToDecimal(result) / 100m : 0m;
    }

    public List<Balance> GetAllBalances()
    {
        var balances = new List<Balance>();

        using var command = _connection.CreateCommand();
        command.CommandText = @"SELECT id, amount, date FROM balance ORDER BY date;";
        using var reader = command.ExecuteReader();
        while (reader.Read())
        {
            balances.Add(new Balance(
                reader.GetInt32(0),
                reader.GetDecimal(1) / 100m,
                reader.GetDateTime(2)
            ));
        }

        return balances;
    }

    public byte GetPayday()
    {
        using var command = _connection.CreateCommand();
        command.CommandText = "SELECT payday FROM settings LIMIT 1;";
        var result = command.ExecuteScalar();
        return result != null ? Convert.ToByte(result) : (byte)10;
    }

    public void ReplacePayday(byte newPayday)
    {
        using var command = _connection.CreateCommand();
        command.CommandText = """
                              INSERT INTO settings (id, payday)
                              VALUES (1, @payday)
                              ON CONFLICT(id) DO UPDATE SET payday = excluded.payday;
                              """;

        command.Parameters.AddWithValue("@payday", newPayday);

        command.ExecuteNonQuery();
        
        DataChanged(this, EventArgs.Empty);
    }

    public List<PlannedPayment> GetAllPlannedPayments()
    {
        var payments = new List<PlannedPayment>();

        using var command = _connection.CreateCommand();
        command.CommandText =
            "SELECT id, amount, name, date_start, date_end, is_subscription, reoccurences, reoccurence_type FROM planned_payment ORDER BY DATETIME(date_start);";
        using var reader = command.ExecuteReader();
        while (reader.Read())
        {
            payments.Add(new PlannedPayment(
                reader.GetInt32(0),
                reader.GetDecimal(1) / 100m,
                reader.GetString(2),
                reader.GetDateTime(3),
                reader.IsDBNull(4) ? null : reader.GetDateTime(4),
                reader.GetBoolean(5),
                reader.IsDBNull(6) ? null : reader.GetInt32(6),
                reader.IsDBNull(7) ? null : (ReoccurenceType)reader.GetInt32(7)
            ));
        }

        return payments;
    }

    public List<PlannedPayment> GetFilteredPlannedPayments()
    {
        var filteredPayments = new List<PlannedPayment>();
        var now = DateTime.Now;

        var nearestPayday = GetNearestPayday(now);

        using var command = _connection.CreateCommand();
        command.CommandText = """
                              SELECT id, amount, name, date_start, date_end, is_subscription, reoccurences, reoccurence_type
                              FROM planned_payment
                              WHERE (
                                  (is_subscription = 0 AND DATETIME(date_start) >= DATETIME(@currentDate) AND DATETIME(date_start) <= DATETIME(@nearestPayday)) OR
                                  (is_subscription = 1 AND (date_end IS NULL OR DATETIME(date_end) >= DATETIME(@currentDate)) AND DATETIME(date_start) <= DATETIME(@nearestPayday))
                              )
                              ORDER BY DATETIME(date_start);
                              """;

        command.Parameters.AddWithValue("@currentDate", now);
        command.Parameters.AddWithValue("@nearestPayday", nearestPayday);

        using var reader = command.ExecuteReader();
        while (reader.Read())
        {
            filteredPayments.Add(new PlannedPayment(
                reader.GetInt32(0),
                reader.GetDecimal(1) / 100m,
                reader.GetString(2),
                reader.GetDateTime(3),
                reader.IsDBNull(4) ? null : reader.GetDateTime(4),
                reader.GetBoolean(5),
                reader.IsDBNull(6) ? null : reader.GetInt32(6),
                reader.IsDBNull(7) ? null : (ReoccurenceType)reader.GetInt32(7)
            ));
        }

        return filteredPayments;
    }

    public DateTime GetNearestPayday(DateTime now)
    {
        var payday = GetPayday();
        var nearestPayday =
            new DateOnly(now.Year, now.Month,
                    payday > DateTime.DaysInMonth(now.Year, now.Month)
                        ? DateTime.DaysInMonth(now.Year, now.Month)
                        : payday)
                .ToDateTime(TimeOnly.MinValue);
        if (now.Day <= payday) return nearestPayday;
        var newDate = new DateOnly(now.Year, now.Month, DateTime.DaysInMonth(now.Year, now.Month)).AddDays(1);
        nearestPayday =
            new DateOnly(newDate.Year, newDate.Month,
                payday > DateTime.DaysInMonth(newDate.Year, newDate.Month)
                    ? DateTime.DaysInMonth(newDate.Year, newDate.Month)
                    : payday).ToDateTime(TimeOnly.MinValue);

        return nearestPayday;
    }

    public void RemovePlannedPayment(int id)
    {
        using var command = _connection.CreateCommand();
        command.CommandText = """
                              DELETE FROM planned_payment
                              WHERE id = @id;
                              """;
        command.Parameters.AddWithValue("@id", id);
        command.ExecuteNonQuery();
        DataChanged(this, EventArgs.Empty);
    }
    
    public event EventHandler DataChanged;
}